An international team of researchers led by Roderic Guigó from the Center for Genomic Regulation made a discovery that Mr. Sherlock Holmes would envy.
It was previously proved that genes remain active for several more days after death. Now, scientists have reported that changes in gene expression caused by death can be used to determine the most accurate time of death.
©Depositphotos / "Anatomy Lesson of Dr. Tulp", Rembrandt Harmenszoon van Rijn, 1632
According to the authors, for observations that will give a hint to criminologists, only body tissue will be needed - the skin or some of the organs. At the same time, it is possible to determine how much time has passed since the moment of death, with greater accuracy than today's standard forensic medical examination allows.
Work began on the Genotype-Tissue Expression Project (GTEx). His goal was to create a reference database for professionals who study how different gene variants affect disease susceptibility and other body indicators.
Collecting this data bank, scientists selected many tissue fragments from a large number of patients. On their examples predispositions to different diseases, the causes of genetic changes and so on were studied.
Since the samples for research were taken from already deceased donors, it was necessary to find out whether changes in gene expression were associated with death or with the time of death, says Roderic Guigó.
Thus, experts could most accurately simulate predictions about which gene variants in different tissues would be associated with various diseases.
To analyze changes in gene expression that are specific for different body tissues after a person’s death, the team studied RNA sequencing data from more than seven thousand samples from 36 different tissues obtained from 540 donors.
In addition, in the course of this work, an interesting detail emerged: the time elapsed since the moment of death affects the expression of genes. Moreover, this effect was different for each fabric.
The reaction to the death of an organism is rather specific to tissues, explains Gigo. For example, over time there was very little change in the activity of the genes of the brain or spleen, but more than 600 of the muscle genes either significantly increased or decreased the activity after a person died.
After analyzing and comparing the possible variants, the authors created models for determining the postmortem interval, based on these very "tissue-specific" changes in gene expression.
In addition, Roderic Guigó and his colleagues developed software that "studied" the models with examples of 399 people. Then they checked how well the machine learning algorithms predict the time of death: they were given various 129 cases to check.
The program successfully coped with the task; Experts note that it is well "notice the details." For example, if after death the activity of genes in the blood was reduced (these genes are involved in the process of producing DNA, the immune response and metabolism) and, at the same time, increased activity of “stressful” genes was observed, this indicated that a person died six hours backwards
Scientists note that most of the changes in the work of genes (both increase and decrease in activity) are observed 7-14 hours after death, and after 14 hours the activity seems to stabilize somewhat.
The researchers also add that their models still need refinement and refinement, after which they can be used in forensic examination.
The colleagues of Roderic Guigó, who did not participate in this work, met results enthusiastically and noted that new methods could be combined with artificial intelligence algorithms - this will further facilitate the task for pathologists and other specialists in this field.
More details about the new technique are described in an article published in the Nature Communications publication.
The illustrations are used in agreement with the Depositphotos photobank
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